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Abstract
Despite decades of research, sand production remains a significant challenge in petroleum industry around the world. Extensive numerical, analytical and experimental studies have been conducted and analysed to address the issue. In particular, analytical solutions have gained significant popularity especially within industry due to the fact that numerical analysis is computationally demanding, time consuming; and solutions are unstable in many instances. Needless to say that input parameters are unavailable in many cases to scarcity of the core samples. Analytical solutions are however much less demanding although they yet need to evolve to represent the rock behaviour more accurately.
Therefore, a new set of closed-form solutions are developed to predict stress-strain distributions around the wellbore drilled in poro-elastoplastic media with strain softening behaviour i.e. rock strength softening is often evident from field observations. Three failure criteria are chosen to model the plastic behaviour: Mohr-Coulomb, Drucker-Prager and Hoek-Brown. A set of hollow cylinder experiments are later conducted under different compression scenarios for validation purposes and both Digital Image Correlation and 3D X-Ray Computed Tomography are performed to image the samples before and after the experiments. An image analysis process converts the obtained images into distinct phases including plastic strain for result analysis. The results of the proposed analytical solutions are compared with the experimental results. The onset of plastic development (sanding) is investigated and good agreement between the model prediction and experimental data is observed.
Finally, the proposed solutions are used in a field application. A well in Bohai Bay in Northeast of China showing sanding issue is selected. Initial acoustic log data along with core analysis data are used to provide the physical parameters for proposed analytical model in order to predict the potential of sanding. The proposed solution showed a significant amount of plastic strain development around the borehole and therefore a wide plastic zone under high drawdown pressure which is confirmed with the field observation for this well.